1. Field of the Invention
This invention relates generally to devices for breaking concrete. More particularly, but not by way of limitation, the present invention relates to a drop hammer for breaking concrete, asphalt, etc. which is mounted to a skid steer or back hoe.
2. Background
When paved surfaces such as roadways or parking lots are in need of repair or resurfacing, there is often a need to break up the existing surface for removal. In the past, this has been accomplished with specialized and dedicated equipment. These dedicated pieces of equipment typically require a substantial investment and are limited to the single task of breaking up a surface.
Previous devices, such as the one disclosed in U.S. Pat. No. 5,607,022 (xe2x80x9cthe ""022 patentxe2x80x9d) have been developed which attach to existing equipment such as a skid steer. These devices reduce the equipment cost but have exhibited limitations in their performance. For example, the device disclosed in the ""022 patent uses a hydraulic cylinder to lift a weight wherein hydraulic fluid is first pumped from a reservoir into the hydraulic cylinder causing the cylinder rod to extend. When the weight reaches a preselected height, a trip switch is activated which opens a dump valve thereby allowing fluid to flow from the hydraulic cylinder back into the reservoir as the cylinder rod is retracted by the falling weight. Unfortunately, the rate at which the weight falls is limited by restrictions on the flow of the hydraulic fluid from the hydraulic cylinder to the reservoir. The flow rate is thus limited by factors such as the diameter and length of the hydraulic lines, some of which are integral to the skid steer. In particular, the hydraulic return line of the skid steer which returns hydraulic fluid to the reservoir often proves to be the limiting factor in determining the drop rate of the weigh. Accordingly, unless a separate hydraulic system is employed, requiring a pump, motor, reservoir, and cooling system, the drop rate is limited by factors which are outside of the control of the supplier of the breaker. A need, therefore, exists for a hydraulic system for a concrete breaker which will support the flow rate of hydraulic fluid necessary to achieve a satisfactory drop rate of the weight, independent of the flow rate sustainable by the skid steer and without substantial additional hydraulic subsystems.
In addition, the hydraulic system disclosed in the ""022 patent is not a closed system. As the cylinder is filled to lift the weight, fluid is drawn from the reservoir, and, conversely, as the weight falls and the cylinder is emptied, fluid is returned to the reservoir. Obviously, the reservoir must be able to accommodate these fluctuations in the volume of fluid stored within the reservoir. This is typically accomplished by venting the reservoir to the atmosphere. Venting in a cyclic hydraulic system, such as the system typically employed in a breaker, causes air to continuously be drawn in to, and subsequently expelled from, the reservoir. This is of particular concern at a construction site where the air may have a relative high concentration of dust and other particulate matter as is usually the case where the existing pavement is being broken and removed. A need also exists, therefore, for a concrete breaker which does not require a reservoir, or if a reservoir is already present on the skid steer, minimizes fluctuations in the fluid level in the reservoir during operation of the breaker.
Finally, there often exists a need to transport, and even operate, a concrete breaker where overhead obstructions are a concern. Previous devices have typically been of a fixed height. Accordingly, a need exists for a concrete breaker wherein the overall height of the device may be adjusted downward for transportation or operation in vertically confirmed spaces, or adjusted upward for more effective operation in spaces where overhead clearance is not a concern.
The present invention provides a device for breaking up a paved surface which satisfies the needs and alleviates the problems discussed above. The inventive apparatus attaches to a host, such as a skid steer or backhoe, having a hydraulic power supply and preferably comprises a closed hydraulic system which includes a regenerative type hydraulic cylinder arrangement adjustably supported within a vertical frame. The cylinder is operably attached to a weight such that when fluid is pumped into a first chamber from the host, a piston disposed between the first chamber and a second chamber drives a rod, thereby lifting a weight. At the same time, the piston forces hydraulic fluid from the second chamber back to the host. Upon reaching a prescribed height, a valve is opened, allowing fluid to flow from the first chamber into the second chamber on the other side of the piston, thereby allowing the weight to drop rapidly under the influence of gravity. This is an important aspect of the present invention because the required volumetric flow rate is very large to allow the weight to fall freely. The rapid flow of fluid from the first chamber into the second chamber is a function of the above described structure of the inventive device and is thus independent of the diameter and length of hydraulic lines provided on the skid steer. A tool attached to the weight strikes the paved surface at the bottom of travel of the weight, breaking up the surface.
Since hydraulic fluid is forced from the second chamber by the piston as fluid is pumped into the first chamber, and likewise, since fluid forced from the first chamber, as the weight falls, fills the second chamber, the volumetric rate of fluid drawn from or returned to a reservoir is reduced to within the host""s operating range.
The regenerative concentric type double hydraulic cylinder arrangement includes a threaded cylindrical outside surface which receives an adjustment nut wherein the vertical position of the cylinder relative to the frame may be adjusted. The overall height of the inventive device may be adjusted to a relatively low position for transportation or operation where overhead clearance is a concern or adjusted to a higher position for more effective breaking where no such concern exists.
It is thus an object of the present invention to provide a device for a breaking up a paved surface which may be attached to existing equipment such as a skid steer or backhoe.
It is a further object of the present invention to provide a device for breaking up a paved surface which incorporates a regenerative double hydraulic cylinder arrangement wherein restrictions in the flow of hydraulic fluid while a weight is dropped, are substantially independent of the hydraulic system of the host skid steer or backhoe thereby allowing the weight to fall at a higher rate than achieved by previous devices.
It is still a further object of the present invention to provide a device for breaking up a paved surface which utilizes a closed hydraulic system such that a reservoir and other necessary related subsystems my be eliminated or, if a reservoir is present, fluctuations in the amount of fluid in the reservoir are reduced to an insignificant level.
It is yet a further object of the present invention to provide a device for breaking up a paved surface wherein the position of the hydraulic cylinder relative to the frame is adjustable to accommodate a variety of operating conditions and to improve transportability of the inventive device.
Further objects, features, and advantages of the present invention will be apparent to those skilled in the art upon examining the accompanying drawings and upon reading the following detailed description of the preferred embodiments.